Use of niobium tungsten oxide materials in the preparation of thermal battery cathode materials

Abstract

The application relates to the technical field of thermal batteries, in particular to application of niobium tungsten oxide material in preparation of a positive electrode material of a thermal battery. 12 WO 33 , Nb 14 W3O 44 or Nb 18 W 16 O 93 . The method can be used for simultaneously synthesizing three different niobium tungsten oxides, the prepared niobium tungsten oxide materials all have the shear-shaped structure special for Wadsley-Roth phase, 3D infinite tunnels are formed in the materials for fast transmission of lithium ions, the three kinds of niobium tungsten oxide materials are high in thermal stability, not easy to dissolve in electrolyte and not easy to absorb water, and all have excellent electrochemical performance, and are applied as the positive electrode material of the thermal battery for the first time.

Description

Technical Field

[0001] This invention relates to the field of thermal battery technology, specifically the application of niobium tungsten oxide materials in the preparation of positive electrode materials for thermal batteries. Background Technology

[0002] In recent years, niobium tungsten oxides have been used as a high-rate lithium-ion battery anode material due to their excellent electrochemical performance. In particular, the article published by an international team in Nature (Niobium tungsten oxides for high-rate lithium-ion energy storage, Griffith et al., Nature, 2018, 559, 556) has demonstrated the unique lithium storage performance of Wadsley-Roth phase niobium tungsten oxides, which has brought widespread attention to the study of niobium tungsten oxides.

[0003] Thermal batteries, as a type of thermally activated storage battery, utilize molten salt electrolytes that are non-conductive at room temperature but become conductive in a molten state at operating temperatures of 350–550°C. They are commonly used in military weapons, aerospace, and nuclear weapons. Continuous technological advancements have driven the development of thermal batteries. However, traditional sulfide cathode materials such as FeS2 have poor thermal stability and are unsuitable for their high operating temperatures; transition metal chlorides such as NiCl2 have high water absorption, easily leading to short circuits and battery failure; and some oxides, such as V2O5, are readily soluble in the electrolyte, hindering stable discharge reactions. Therefore, with the increasing demands for miniaturization, high capacity, and high energy density in thermal batteries, it is necessary to develop novel thermal battery cathode materials to meet the needs of the new era. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide the application of niobium tungsten oxide materials in the preparation of cathode materials for thermal batteries. The method of this invention can simultaneously synthesize three different niobium tungsten oxides, namely Nb... 12 WO 33 、Nb 14 W3O 44 、Nb 18 W 16 O 93 The niobium tungsten oxide materials obtained all have the shear-like structure unique to the Wadsley-Roth phase, forming 3D infinite tunnels inside to facilitate rapid lithium-ion transport. The three niobium tungsten oxide materials have high thermal stability, are not easily soluble in electrolytes, and do not absorb water, all exhibiting excellent electrochemical performance, and have been used as cathode materials for thermal batteries for the first time.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention protects the application of niobium tungsten oxide materials in the preparation of cathode materials for thermal batteries, wherein the niobium tungsten oxide material is Nb 12 WO 33 、Nb 14 W3O 44 or Nb 18 W 16 O 93 This application is being disclosed for the first time under this application.

[0007] The preferred application method is as follows:

[0008] Using niobium tungsten oxide as the positive electrode material of a thermal battery, the niobium tungsten oxide material is mixed with a conductive agent to obtain an active niobium tungsten oxide material. The conductive agent has electrical conductivity and can be selected from metals such as silver powder and nickel powder, or from carbon materials such as graphene and carbon nanotubes. The principle is to improve the conductivity between powders by mixing with the conductive agent.

[0009] LiCl-KCl electrolyte is mixed with binder MgO, and the binder is bonded by the capillary action of MgO to obtain a bonded electrolyte.

[0010] Niobium tungsten oxide active material is mixed with binder electrolyte to obtain positive electrode mixed active material;

[0011] In a dry environment with a dew point temperature below -50°C, current collector graphite paper, Li-B alloy sheet, bonding electrolyte, and positive electrode mixed active material are sequentially placed into a mold. The current collector graphite paper is similar to the positive and negative electrode shells of a lithium battery, and its function is the same as that of a stainless steel sheet. The Li-B alloy sheet is the negative electrode sheet. Then they are pressed together to obtain a thermal battery.

[0012] Preferably, the mass ratio of niobium tungsten oxide material to conductive agent is 5-15:1; the mass ratio of electrolyte to binder is 1-1.5:1; and the mass ratio of niobium tungsten oxide active material to binder electrolyte is 8-9:1-2.

[0013] Preferably, the niobium tungsten oxide material is a shear-structured particle with a crystal length of 2-3 μm and a crystal diameter of 5-10 μm. Too small a nanoscale has a low volume density, high cost, and poor stability and sustainability. On the other hand, micron-sized niobium tungsten oxide and its special structure have a high lithium-ion diffusion coefficient and extremely high volumetric capacity and rate performance.

[0014] Preferably, the niobium tungsten oxide material is prepared according to the following steps:

[0015] Battery-grade Nb2O5 and nano WO3 were mixed, ground, and then sieved through a 300-mesh sieve to obtain a mixed powder.

[0016] The mixed powder was heat-treated to obtain three niobium-tungsten oxide materials, the niobium-tungsten oxide material being Nb12 WO 33 、Nb 14 W3O 44 or Nb 18 W 16 O 93 .

[0017] Preferably, when the niobium tungsten oxide material is Nb 12 WO 33 At that time, the molar ratio of Nb2O5 to WO3 was 5.75 to 6.25:1.

[0018] Preferably, when the niobium tungsten oxide material is Nb 14 W3O 44 At that time, the molar ratio of Nb2O5 to WO3 was 2.0 to 2.45:1.

[0019] Preferably, when the niobium tungsten oxide material is Nb 18 W 16 O 93 At that time, the molar ratio of Nb2O5 to WO3 was 0.45 to 0.6:1.

[0020] Preferably, the heat treatment conditions are: heating and holding at 950-1050℃ for 24-30 hours in an air atmosphere. The temperature and time of this application have been screened. Too low a temperature will result in low purity of the synthesized product and more impurity phases, while too high a temperature will result in the product sticking to the wall, uneven particle size, and poor crystallinity of the product.

[0021] Preferably, niobium-tungsten oxide materials all possess a Wadsley-Roth phase shear structure, forming 3D infinite tunnels within to facilitate rapid lithium-ion transport; Nb 12 WO 33 The structural feature is (3×4). ∞ ReO3; Nb 14 W3O 44 The structural feature is (4×4). ∞ ReO3; Nb 18 W 16 O 93 The structural feature is a 1×3×1 superstructure composed of twisted octahedrons of the TTB phase.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention uses a high-temperature solid-state method to prepare niobium-tungsten oxide. Under high-temperature conditions, niobium oxide and tungsten oxide crystals grow in an orderly manner, forming an octahedral structure and connecting into blocks through shared corners, constituting (n×m). ∞The ReO3 unit structure ultimately crystallizes into a composite niobium-tungsten oxide, and the drawbacks of solid-state reactions are mitigated by reducing the size of the raw materials and extending the calcination time. This invention offers low raw material costs, simple operation, high yield, and the ability to synthesize multiple niobium-tungsten oxides simultaneously.

[0024] Currently disclosed (4×5) ∞ ReO3 type Nb 16 W5O 55 and (5×5) ∞ ReO3 type Nb 18 W8O 69 In the preparation methods of niobium tungsten oxides, the synthesis temperature cannot be unified and needs to be synthesized under different calcination temperature conditions. However, the three niobium tungsten oxides of this invention can be synthesized at the same temperature, and (3×4) ∞ Nb of ReO3 12 WO 33 and (4×4) ∞ Nb of ReO3 14 W3O 44 Its volume expansion rate is relatively small. A smaller volume expansion rate results in better cycle stability and more stable electrochemical performance. Furthermore, this characteristic also contributes to more stable discharge in the high-temperature environment of a thermal battery, reducing the impact of high temperatures on electrochemical performance.

[0025] 2. Using the niobium-tungsten oxide synthesized in this invention as the positive electrode material, and matching it with a binary LiCl-KCl electrolyte and a Li-B alloy negative electrode, a thermal battery is prepared and applied. The core component of the thermal battery is the single cell, which mainly consists of current collectors, electrode plates (the positive electrode is usually made of active material through a powder compaction process, and the negative electrode is a Li metal alloy), and molten salt electrolyte. At room temperature, the solid molten salt electrolyte has very low conductivity and is non-conductive, remaining in a storage state. Under operating conditions (temperature between 350-550℃), the molten salt electrolyte is heated to a molten state using a heating system, providing ion transport channels for the positive and negative electrodes, thereby enabling high-power discharge.

[0026] 3. The niobium tungsten oxide material synthesized by this invention has high purity and good crystallinity. This method can obtain three types of niobium tungsten oxide materials, save synthesis time, increase production efficiency, and is suitable for the preparation of multiple active materials for thermal battery cathode materials. It can achieve large-scale, high-efficiency production and meet the demand for thermal battery cathode materials. Attached Figure Description

[0027] Figure 1 The three niobium tungsten oxides (Nb) synthesized in Examples 1-3 of this invention 12 WO 33 、Nb 14 W3O 44 、Nb 18W 16 O 93 XRD patterns of the image and SEM images with dimensions of 5μm to 10μm.

[0028] Figure 2 XPS spectra of the three niobium tungsten oxides synthesized in Examples 1-3 of this invention.

[0029] Figure 3 This is a schematic diagram of the crystal structure of the three niobium tungsten oxides synthesized in Examples 1-3 of the present invention.

[0030] Figure 4 The three niobium tungsten oxide materials synthesized in Examples 1-3 of this invention were used to prepare single-cell thermal batteries at 500 mAg. -1 Discharge curves at current density.

[0031] Figure 5 The three niobium tungsten oxide materials synthesized in Examples 1-3 of this invention are used to prepare single-cell thermal batteries with a discharge current of 500 mAg. -1 The pulse current is 2Ag -1 Pulse discharge and polarization internal resistance at current density. Detailed Implementation

[0032] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0033] Considering the excellent thermal stability and electrochemical performance of niobium tungsten oxide materials, this application is the first to use them as positive electrode materials for thermal batteries. At the same time, considering that the preparation methods of niobium tungsten oxide materials in the prior art are complicated and the preparation cost is high, this application provides a novel preparation method for niobium tungsten oxide materials.

[0034] This application discloses for the first time the application of niobium tungsten oxide as a positive electrode material for thermal batteries. In the prior art, niobium tungsten oxide is mainly used as a negative electrode material for lithium-ion batteries. Compared with lithium-ion batteries, thermal batteries differ in the following ways: the electrolyte of thermal batteries is a solid molten salt electrolyte at room temperature, while that of lithium-ion batteries is a liquid organic solvent lithium hexafluorophosphate; the negative electrode material of thermal batteries is mainly Li-B alloy, while that of lithium-ion batteries is mainly graphite; the positive electrode material of thermal batteries is mostly transition metal sulfides, chlorides, oxides, fluorides, etc., while that of lithium-ion batteries is mainly lithium iron phosphate; the electrode preparation method of thermal batteries is mostly powder compaction process, while that of lithium-ion batteries mainly adopts thin film coating method; the operating temperature of thermal batteries is higher, between 350-550℃, while the operating temperature of lithium-ion batteries is mainly in the room temperature range.

[0035] Existing technology application number CN202110210241.9, entitled "Micron-shaped rod-shaped niobium tungsten oxide and its preparation method and application", describes a method for preparing micron-shaped niobium tungsten oxide, including the following steps: calcining NbC in air at 800–1100℃ for 5–15 h, then mixing it with WO3, followed by calcination at 1100–1300℃ for 12–30 h to obtain niobium tungsten oxide; this method requires two calcinations and is cumbersome. Application number CN201811196582.X, entitled "A high-rate niobium tungsten oxide fast charging electrode material and its preparation method and application", describes a method for preparing niobium tungsten oxide, including the following steps: mixing and grinding NbO2 and WO2, pressing them into blocks, and heating to 1200℃ to obtain NbO2. 16 W5O 55 The two oxide raw materials used in this method are expensive, the heating temperature is too high, and the preparation cost is high. Application number CN202010759380.2, entitled "Niobium-Tungsten Oxide Electrode Material and Its Preparation and Application," describes a method for preparing niobium-tungsten oxide electrode material, including the following steps: Niobium salt, hydrofluoric acid, isopropanol, and tungsten salt are stirred evenly at room temperature and heated to 180-220℃, maintained for 12-48 hours. After the mixed solution cools, the powder is collected, washed, dried, and calcined at 850-950℃ to obtain W6Nb. 14 O 53 This method involves cumbersome preparation steps and produces small quantities.

[0036] It is evident that, given the high requirements for active materials in thermal battery materials, existing synthesis methods are cumbersome, hydrothermal methods have low yields, and solid-state methods often require secondary calcination, with expensive raw materials and excessively high calcination temperatures. Therefore, a novel method is needed to meet the demands for high-volume, high-efficiency production of thermal battery electrode materials.

[0037] Compared with existing technologies, this application also provides a novel method for preparing niobium tungsten oxide materials. The method uses battery-grade Nb₂O₅ and nano-WO₃ as raw materials, which are mixed and then heat-treated. By adjusting the molar ratio of Nb₂O₅ to WO₃, three different niobium tungsten oxide materials can be obtained, namely Nb₂O₅, WO₃, and WO₃. 12 WO 33 、Nb 14 W3O 44 or Nb 18 W 16 O 93 The preparation method of this application has high synthesis efficiency and low cost, and can obtain three different niobium tungsten oxide materials, overcoming the technical defects of existing preparation methods.

[0038] The technical solution of this application will be further explained and illustrated below with examples, as detailed below:

[0039] Example 1

[0040] Nb 12 WO 33 The preparation method of niobium tungsten oxide includes the following steps:

[0041] Step 1: Weigh 6.37944g of battery-grade Nb2O5 and 0.92736g of nano WO3 (molar ratio of 6:1), put them into an agate mortar and grind them by hand for 15 minutes to mix them evenly and obtain a mixed powder.

[0042] Step 2: Transfer the mixed powder from Step 1 to an alumina crucible, and gently shake the crucible to compact the powder. Place the crucible in a muffle furnace, set the heating rate to 5℃ / min, heat to 1000℃ and hold for 28 hours, then cool to room temperature with the furnace to obtain Nb. 12 WO 33 Niobium-tungsten oxide.

[0043] Example 2

[0044] Nb 14 W3O 44 The preparation method of niobium tungsten oxide includes the following steps:

[0045] Step 1: Weigh 5.58201g of battery-grade Nb2O5 and 2.08656g of nano WO3 (molar ratio of 7:3), put them into an agate mortar and grind them by hand for 20 minutes to mix them evenly and obtain a mixed powder.

[0046] Step 2: Transfer the mixed powder from Step 1 to an alumina crucible, and gently shake the crucible to compact the powder. Place the crucible in a muffle furnace, set the heating rate to 5℃ / min, heat to 1000℃ and hold for 28 hours, then cool to room temperature with the furnace to obtain Nb. 14 W3O 44 Niobium-tungsten oxide.

[0047] Example 3

[0048] Nb 18 W 16 O 93 The preparation method of niobium tungsten oxide includes the following steps:

[0049] Step 1: Weigh 4.78458g of battery-grade Nb2O5 and 7.41888g of nano WO3 (molar ratio of 9:16), put them into an agate mortar and grind them by hand for 20 minutes to mix them evenly and obtain a mixed powder.

[0050] Step 2: Transfer the mixed powder from Step 1 to an alumina crucible, and gently shake the crucible to compact the powder. Place the crucible in a muffle furnace, set the heating rate to 5℃ / min, heat to 1000℃ and hold for 28 hours, then cool to room temperature with the furnace to obtain Nb. 18 W 16 O 93 Niobium-tungsten oxide.

[0051] Example 4

[0052] Nb 12 WO 33 Niobium tungsten oxide, Nb 14 W3O 44 Niobium tungsten oxide, Nb 18 W 16 O 93 The preparation method for simultaneous preparation of niobium-tungsten oxide includes the following steps:

[0053] Step 1: Weigh out battery-grade Nb2O5 and nano WO3 according to the corresponding molar ratios of 6:1, 7:3, and 9:16 respectively, then put them into an agate mortar in batches and grind them by hand for 20 minutes to mix them evenly, so as to obtain three mixed powders.

[0054] Step 2: Transfer the three mixed powders from Step 1 into three alumina crucibles respectively, and gently vibrate the crucibles to compact the powder inside. Place the three crucibles into a muffle furnace at the same time, set the heating rate to 5℃ / min, heat to 1000℃ and hold for 30h, and then cool to room temperature with the furnace to obtain three niobium tungsten oxides.

[0055] Example 5

[0056] Nb 12 WO 33 The preparation method of niobium tungsten oxide includes the following steps:

[0057] Step 1: Weigh 6.11363g of battery-grade Nb2O5 and 0.92736g of nano WO3 (molar ratio of 5.75:1), put them into an agate mortar and grind them by hand for 15 minutes to mix them evenly and obtain a mixed powder.

[0058] Step 2: Transfer the mixed powder from Step 1 to an alumina crucible, and gently shake the crucible to compact the powder. Place the crucible in a muffle furnace, set the heating rate to 5℃ / min, heat to 1050℃ and hold for 24 hours, then cool to room temperature with the furnace to obtain Nb. 12 WO 33 Niobium-tungsten oxide.

[0059] Example 6

[0060] Nb 12 WO 33 The preparation method of niobium tungsten oxide includes the following steps:

[0061] Step 1: Weigh 6.64525g of battery-grade Nb2O5 and 0.92736g of nano WO3 (molar ratio of 6.25:1), put them into an agate mortar and grind them by hand for 15 minutes to mix them evenly and obtain a mixed powder.

[0062] Step 2: Transfer the mixed powder from Step 1 to an alumina crucible, and gently shake the crucible to compact the powder. Place the crucible in a muffle furnace, set the heating rate to 5℃ / min, heat to 950℃ and hold for 30 hours, then cool to room temperature with the furnace to obtain Nb. 12 WO 33 Niobium-tungsten oxide.

[0063] Example 7

[0064] Nb 14 W3O 44 The preparation method of niobium tungsten oxide includes the following steps:

[0065] Step 1: Weigh 4.78458g of battery-grade Nb2O5 and 2.08656g of nano WO3 (molar ratio of 2:1), put them into an agate mortar and grind them by hand for 20 minutes to mix them evenly and obtain a mixed powder.

[0066] Step 2: Transfer the mixed powder from Step 1 to an alumina crucible, and gently shake the crucible to compact the powder. Place the crucible in a muffle furnace, set the heating rate to 5℃ / min, heat to 1050℃ and hold for 24 hours, then cool to room temperature with the furnace to obtain Nb. 14 W3O 44 Niobium-tungsten oxide.

[0067] Example 8

[0068] Nb 14 W3O 44 The preparation method of niobium tungsten oxide includes the following steps:

[0069] Step 1: Weigh 5.8611g of battery-grade Nb2O5 and 2.08656g of nano WO3 (molar ratio of the two is 2.45:1), put them into an agate mortar and grind them by hand for 20 minutes to mix them evenly and obtain a mixed powder.

[0070] Step 2: Transfer the mixed powder from Step 1 to an alumina crucible, and gently shake the crucible to compact the powder. Place the crucible in a muffle furnace, set the heating rate to 5℃ / min, heat to 950℃ and hold for 30 hours, then cool to room temperature with the furnace to obtain Nb. 14 W3O 44 Niobium-tungsten oxide.

[0071] Example 9

[0072] Nb 18 W 16 O 93 The preparation method of niobium tungsten oxide includes the following steps:

[0073] Step 1: Weigh 3.8276g of battery-grade Nb2O5 and 7.41888g of nano WO3 (molar ratio of 0.45:1), put them into an agate mortar and grind them by hand for 20 minutes to mix them evenly and obtain a mixed powder.

[0074] Step 2: Transfer the mixed powder from Step 1 to an alumina crucible, and gently shake the crucible to compact the powder. Place the crucible in a muffle furnace, set the heating rate to 5℃ / min, heat to 1050℃ and hold for 24 hours, then cool to room temperature with the furnace to obtain Nb. 18 W 16 O 93 Niobium-tungsten oxide.

[0075] Example 10

[0076] Nb 18 W 16 O 93The preparation method of niobium tungsten oxide includes the following steps:

[0077] Step 1: Weigh 5.103552g of battery-grade Nb2O5 and 7.41888g of nano WO3 (molar ratio of 0.6:1), put them into an agate mortar and grind them by hand for 20 minutes to mix them evenly and obtain a mixed powder.

[0078] Step 2: Transfer the mixed powder from Step 1 to an alumina crucible, and gently shake the crucible to compact the powder. Place the crucible in a muffle furnace, set the heating rate to 5℃ / min, heat to 950℃ and hold for 30 hours, then cool to room temperature with the furnace to obtain Nb. 18 W 16 O 93 Niobium-tungsten oxide.

[0079] Examples 1-10 of this invention all yielded niobium-tungsten oxides with excellent electrochemical performance for use in thermal batteries. The niobium-tungsten oxides from Examples 1-3 are used as examples for further research, and the specific research methods and results are shown below:

[0080] 1. Structural study:

[0081] Figure 1 The XRD patterns and SEM images of the three niobium tungsten oxides synthesized in Examples 1-3 are shown below; Figure 1 Figures (1), (2), and (3) show the XRD patterns of three niobium tungsten oxides. The results show that all three products have a very high degree of overlap with the standard card, and the crystal planes corresponding to the crystal diffraction peaks are consistent with the information on the standard card, which fully demonstrates that high-purity niobium tungsten oxides were obtained. Their SEM images also show the shear-like structure unique to Wadsley-Roth phase niobium-based polymers, such as... Figure 1 As shown in (4), (5), and (6), Nb 12 WO 33 Niobium tungsten oxide, Nb 14 W3O 44 Niobium tungsten oxide, Nb 18 W 16 O 93 The morphology of niobium tungsten oxide resembles that of scissors cutting, and the voids inside the grains provide a fast channel for lithium-ion transport.

[0082] Figure 2 The XPS spectra of the three niobium tungsten oxides synthesized in Examples 1-3 show that the Nb element in these three products is in the +5 valence state and the W element is in the +6 valence state, which proves that the target niobium tungsten oxide products were successfully synthesized.

[0083] Figure 3The diagram shows the crystal structures of the three niobium-tungsten oxides synthesized in Examples 1-3. 12 WO 33 It is a monoclinic crystal system in space group C2, and its structural characteristic is (3×4). ∞ The basic ReO3 unit is composed of NbO6 octahedrons and WO3 tetrahedrons; the difference is that NbO6... 14 W3O 44 The space group is I4 / m in the plane of the ab axis, connected by (Nb / W)O6 octahedral chains and WO3 tetrahedrals. The (Nb / W)O6 octahedrals are shared outward along the ab plane, and the structural feature is (4×4). ∞ ReO3; Nb 18 W 16 O 93 It is a monoclinic crystal system, Pbam space group, and a 1×3×1 superstructure composed of twisted octahedra of the TTB phase. These unique crystal structures allow for the existence of infinite three-dimensional tunnels within it, enabling rapid intercalation reactions of lithium ions and resulting in excellent electrochemical performance. In contrast, the negative electrode material of thermal batteries is typically a Li metal alloy, which also requires the material to provide Li during battery operation. + The rapid migration channels, coupled with the excellent thermal stability of niobium tungsten oxide, give them certain advantages as cathode materials for thermal batteries.

[0084] 2. Electrochemical performance study:

[0085] Using the three niobium tungsten oxide materials synthesized in Examples 1-3 as positive electrode materials for thermal batteries, in a dry environment with a dew point temperature below -50°C, the materials were weighed according to a mass ratio of niobium tungsten oxide active material (with 10% mass fraction of conductive agent Ni powder) to EB (LiCl-KCl electrolyte and MgO binder) of 8:2, and ground in an agate mortar for 10 minutes to obtain a positive electrode mixed active material; then, graphite paper with a diameter of 18 mm, Li-B alloy sheet, 0.36 g of EB, and 0.3 g of positive electrode mixed active material were placed in a mold in sequence, and the above sample was pressed into single-cell battery particles with a diameter of 18 mm and a thickness of about 3 mm by a powder compaction process.

[0086] Electrochemical testing of individual cells was conducted in an argon-filled glove box. A clamp was added to the furnace for heating and connection to external testing instruments. The test temperature was 500℃. Electrochemical testing was performed on the Blue Electric testing system with a constant current discharge current density of 500 mAg. -1 .

[0087] Figure 4 For Nb 12 WO 33 、Nb 14 W3O 44 、Nb18 W 16 O 93 At 500mAg -1 The constant current discharge curves at current density show that all three niobium-tungsten oxides have open-circuit voltages above 2.0V and operating voltages above 1.5V; at a cutoff voltage of 1.0V, Nb 12 WO 33 、Nb 14 W3O 44 、Nb 18 W 16 O 93 They each have 1074mAh g -1 882.4mAhg -1 965.2mAhg -1 High specific capacity.

[0088] The pulse performance testing of individual cells was also conducted on the Blue Lightning testing system, with a constant current discharge current density of 500 mAg. -1 The pulse current is 4 times 2Ag -1 The formula for calculating the polarization resistance is R = ▽V / ▽I, where the current density is 0.

[0089] Figure 5 The following are pulse discharge and polarization resistance diagrams of the niobium tungsten oxide synthesized in Examples 1-3. It can be seen that Nb 12 WO 33 The polarization resistance is minimal, not exceeding 0.5Ω; Nb 14 W3O 44 Secondly, the internal resistance stabilizes at 1Ω; Nb 18 W 16 O 93 The polarization resistance is the largest, initially stable at 1Ω, but reaching 1.8Ω at 2000 seconds. This is because oxides have poor conductivity and high polarization resistance, which is quite common and can often be improved by adding conductive agents and carbon coating.

[0090] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications should fall within the scope of the present invention as defined by the appended claims and their equivalents.

Claims

1. The application of niobium-tungsten oxide materials in the preparation of cathode materials for thermal batteries, characterized in that, Niobium tungsten oxide material is Nb 12 WO 33 、Nb 14 W3O 44 or Nb 18 W 16 O 93 .

2. The application of the niobium-tungsten oxide material according to claim 1 in the preparation of cathode materials for thermal batteries, characterized in that, The application method is as follows: Using niobium tungsten oxide as the positive electrode material of a thermal battery, the niobium tungsten oxide material is mixed with a conductive agent to obtain an active niobium tungsten oxide material; LiCl-KCl electrolyte is mixed with binder MgO to obtain a bound electrolyte; Niobium tungsten oxide active material is mixed with binder electrolyte to obtain positive electrode mixed active material; In a dry environment with a dew point temperature below -50°C, current collector graphite paper, Li-B alloy sheet, binder electrolyte, and positive electrode mixed active material are sequentially placed into a mold and then pressed together to obtain a thermal battery.

3. The application of the niobium-tungsten oxide material according to claim 2 in the preparation of cathode materials for thermal batteries, characterized in that, The mass ratio of niobium tungsten oxide material to conductive agent is 5-15:1; the mass ratio of electrolyte to binder is 1-1.5:1; and the mass ratio of niobium tungsten oxide active material to binder electrolyte is 8-9:1-2.

4. The application of the niobium-tungsten oxide material according to claim 1 in the preparation of cathode materials for thermal batteries, characterized in that, Niobium tungsten oxide materials are shear-structured particles with a crystal length of 2-3 μm and a crystal diameter of 5-10 μm.

5. The application of the niobium-tungsten oxide material according to claim 1 in the preparation of cathode materials for thermal batteries, characterized in that, Niobium tungsten oxide materials are prepared according to the following steps: Battery-grade Nb2O5 and nano WO3 were mixed, ground, and then sieved through a 300-mesh sieve to obtain a mixed powder. The mixed powder was heat-treated to obtain three niobium-tungsten oxide materials, the niobium-tungsten oxide material being Nb 12 WO 33 、Nb 14 W3O 44 or Nb 18 W 16 O 93 .

6. The application of the niobium-tungsten oxide material according to claim 5 in the preparation of cathode materials for thermal batteries, characterized in that, When the niobium tungsten oxide material is Nb 12 WO 33 At that time, the molar ratio of Nb2O5 to WO3 was 5.75 to 6.25:

1.

7. The application of the niobium-tungsten oxide material according to claim 5 in the preparation of cathode materials for thermal batteries, characterized in that, When the niobium tungsten oxide material is Nb 14 W3O 44 At that time, the molar ratio of Nb2O5 to WO3 was 2.0 to 2.45:

1.

8. The application of the niobium-tungsten oxide material according to claim 5 in the preparation of cathode materials for thermal batteries, characterized in that, When the niobium tungsten oxide material is Nb 18 W 16 O 93 At that time, the molar ratio of Nb2O5 to WO3 was 0.45 to 0.6:

1.

9. The application of the niobium tungsten oxide material according to claim 5 in the preparation of positive electrode material for thermal batteries, wherein the heat treatment conditions are: heating and holding at 950-1050°C for 24-30 hours in an air atmosphere.

10. The application of the niobium-tungsten oxide material according to claim 1 in the preparation of cathode materials for thermal batteries, characterized in that, Nb 12 WO 33 The structural feature is (3×4). ∞ ReO3; Nb 14 W3O 44 The structural feature is (4×4). ∞ ReO3; Nb 18 W 16 O 93 The structural feature is a 1×3×1 superstructure composed of twisted octahedrons of the TTB phase.

Images